9/10.
Other than the essay "On Earthquakes", which showcases Seneca's interest in the natural sciences, this collection of Seneca's letters and essays is a treasture of wisdom. Even with the translation, you can still feel the elegance of Seneca's Latin prose and the aristocratic sense of Rome.
What is this aristocratic sense? What is aristocracy? It is the rule of the best, the rule of the nobles. Nobility prides itself on noblesse oblige — the obligations of nobility. Due to their noble blood and honorable heritage, the nobles feel a duty to live up to something. And the Stoics called that something virtue. Virtue for the Stoics — similar to the Christian view, but certainly not the same — means the complete control of the passions by reason. Another way of talking about virtue — this view completely contrary to the Christian view — means yielding to the passions in accordance with Nature, but no more.
Nature? Yes, we must not overindulge our passions above their natural purpose. Let's give some examples.
Think about food. Its purpose is to provide nourishment, health, and energy. Natural deviations from this include overeating, undereating, and eating food that is unnatural/deleterious to our bodies. Therefore, we must avoid indulgence, avoid industrially-produced crap, and avoid starving ourselves unnecessarily. How can we reach this state? Physiologically, we can wean ourselves off of the food we are addicted to and fast (intermittently or otherwise) every week. If we cultivate this discipline (enacted externally in many religions, e.g. Orthodoxy), we will strengthen our will and decrease our servitude to passion.
Or take sex. Our society is sexually addicted — in an unnatural way. And that is the problem. Constant masturbatory stimulation to the most unnatural and depraved acts possible, women dressed provocatively everywhere they go, and a desire to fornicate — for fornication itself — are all extremely displaced from Nature's purpose of sex. Sex is for procreation. Procreation happens in marriage. Any other ejaculatory activity is wasting one's seed and sapping one's testosterone. It has been shown that masturbation destroys grey matter in your prefrontal cortex, makes you anxious and depressed, and destroys your sensitivity to the actual act of sex when you have it (erectile dysfunction). This is all due to deviating from Nature's purpose. Thus, we must understand sex as healthy, but only healthy in the way Nature created it: procreation. Unnecessary sexual desire will distract us and present our mind's eye with a barrage of reviling and distracting images, which will disturb our peace of mind with depravity.
One can apply this principle to rest (not too long, not too short), exercise (regular, but with rest days), drugs (avoid them entirely), sorrow (do not wallow in it, cut it out after its proper time), and anger (feel it when it happens, but do not inflame it by constantly thinking of the object which incenses you).
When we follow the course of Nature, we will become free — not "free" politically nor free to be the slave of our passions (the eternal slavery of modern man), but free to be self-sufficient and non-reactive. If you are a Skinnerian rat, ever conditioned to external stimuli, then you will never be in control of yourself. If you see a piece of candy, you won't be able to resist eating it. If you see a sexually attractive image, you won't be able to look away. If you are a slave of alcohol or coffee, you won't be able to live without it. You will be fragile — weak. If your external circumstances falter, then you will suffer.
That is the loss of all freedom. The goal of the philosopher — he who pursues wisdom — is to be separate from all external circumstances. This is the optimal state of existence. If one reaches this state, you will have no risk of compromising your values and beliefs, of lying, of cowardice in the face of battle. You will become like Socrates, taking the cup of hemlock with joy. How do you do this? Moderation, temperance, prudence. "The golden mean," as Aristotle said. Watch for overindulgence — in drink, lust, food, anger, or any other destructive substance or emotion — and once you detect it, cut it out.
"But I can't cut it out: it is too hard!". Externally cut it out, which will then modify your habits through necessity. For example, do not buy the food you are addicted to. Do not buy sugary food. If you have food items in your house that make you hate yourself after you consume them, then throw them away or give them away. Block pornographic websites that you habitually visit. Get a lockbox and put your wallet in it for the day if you are a spendthrift. Do not save your credit card on Amazon. Work out regularly with a friend, and make a promise that you will pay them $50 if you do not work out.
Thus you will take the first step toward changing your habits. From there, it will be easier to achieve an internal sense of self-control. Combine this sense of inner self-control with a sense of aristocratic duty — the duty of living up to your potential and ancestors. For they were tougher than you. How can you be so weak? How can you not take four hours out of your life to lift every week, when your ancestors were lifting hay bales for hours every day? How can you not simplify your diet to not include sugar and oily crap, when your ancestors were satisfied with bread, butter, vegetables, and meat? How can you not take one hour out of your day to read, when your ancestors knew five languages and had mastered Greek, Latin, and their nationality's literature? Raise your mind to the heights of those who came before, master your passions, and climb the mountains of man. Save yourself from endless self-pity and regret; replace them with a radiant cheerfulness and strength. Break the shackles of low expectations and rise to what you were meant to be: a noble.